1. Field of the Invention
This application claims priority under 35 U.S.C. 119 from European Patent Application No. 04 018 283.4, filed on Aug. 2, 2004.
The invention relates to a method for controlling a variable of a transmission, to a fixed network element and a network control element, wherein data units (e.g., Transport Blocks) are sent using a time diversity.
2. Description of the Related Art
The invention relates to power control in a radio access network such as UTRAN (UMTS Radio Access Network), for example. There are basically two main forms of power control in UTRAN, namely open loop power control (which is usually used in an initial stage) and closed loop power control (which is used during an ongoing communication). The closed loop power control is divided into the so-called inner loop power control and the so-called outer loop power control. The inner loop power control is performed between the base station (Node B) and the User Equipment (UE) based on the Signal to Interference Ratio (SIR), such that the current SIR reaches a target SIR. The target SIR is determined in the outer loop power control by a Radio Network Controller (RNC). The target SIR is determined based on the Block Error Rate (BLER). That is, the Outer-Loop Power Control (OLPC) checks the BLER ratio of the Transport Blocks (TB) compared to a target BLER during an OLPC update period and performs a so-called target-UP step, if the observed BLER is higher than the observed target, and otherwise a so-called target-DOWN step. Based on this, the RNC forwards a new target SIR to the Node B and the UE. The target BLER used by the RNC is also determined based on the required quality of service for a particular service etc.
Recently, new measures to increase the data rate in UMTS in downlink and uplink direction have been proposed, namely High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA). The invention is in particular directed to HSUPA, but not limited thereon. In HSUPA is an enhanced uplink transport in WCDMA (Wideband Code Division Multiple Access) in which a so-called Enhanced Dedicated Channel (E-DCH) is used, which includes time-diversity transmission techniques. These time diversity transmission techniques may include ARQ (Automatic Repeat request), HARQ (Hybrid ARQ), HARQ+Chase Combining, HARQ+IR (Incremental Redundancy) These ARQ schemes perform a repetition of sending of a Transport Block (TB) in case the TB was corrupted or the like.
Due to the retransmissions performed on the E-DCH, when the OLPC algorithm described above is applied without any modification, a problem may occur that the BLER target will not be met accurately. That is, for example, unnecessary high transmission power will be wasted. In addition, this problem may also occur to other variables in the control in HSUPA and the like which depend on the BLER target.